Scanning electron microscopes (SEMs), transmission electron microscopes (TEMs), etc. are widely used for observing minute areas on objects. In such devices, images of a sample are captured generally by keeping the sample atmosphere (atmosphere around the sample) in a vacuum state by vacuum evacuating a second housing storing the sample. Meanwhile, there are increasing needs for observing samples that are damaged or changed by the vacuum (biochemical samples, liquid samples, etc.) by use of an electron microscope. In recent years, SEM devices, sample holding devices, etc. that make it possible to observe samples (observation targets) under the atmospheric pressure are being developed.
In principle, such devices separate the vacuum state and the atmospheric state from each other by arranging a thin film that allows through the electron beam between the electronic optical system and the sample. The arrangement of the thin film between the electronic optical system and the sample is common to such devices.
Patent Literatures 1-3 have described atmospheric pressure SEM devices in which the thin film allowing through the electron beam is arranged in the vicinity of the sample and is used for separating the vacuum state and the atmospheric pressure state from each other for the purpose of observing a sample or liquid placed under the atmospheric pressure.